1. Field of the Invention
The present disclosure relates generally to cone beam computed tomography, and more particularly, to a method and system for cone beam x-ray source and detector arrangement in computed tomography systems.
2. Background of the Invention
Cone beam computed tomography (“CBCT”) is utilized for obtaining tomographic radiographic images of the dento-maxillo facial region. By combining CBCT with x-ray detection units, tomographic radiographic images of the dento-maxillo facial region are obtained by acquiring a sequence of two-dimensional radiographic images during rotation of an arm around the anatomical part of interest. The existing systems can be implemented for both a standing patient, as illustrated in FIG. 1A, and a sitting patient, as illustrated in FIG. 1B. For example, existing cone beam 14 systems include an arm 10, an arm support structure 11, an x-ray source 12, an x-ray image detector 13, electric motors to actuate rotational movements and vertical transitional movements, motor control electronic circuitry, electronic circuitry to control and drive the x-ray source 12 and x-ray image detector 13, and a computer for controlling the electronic circuitry, and processing and displaying acquired data and images. The arm 10 is translatable along the vertical axis to adjust, for example, to the patient's height, and can be vertically rotated 360 degrees around a rotational axis which corresponds to the anatomical target.
Both the x-ray source 12 and x-ray image detector 13 are rigidly connected on opposite ends of the arm 10, and are arranged to rotate about a vertical axis. However, with this arrangement, both the x-ray source 12 and the x-ray image detector 13 must be sufficiently far from the anatomical part of interest, for example, a patient's head, so as not to interfere with the patient during rotation, for example, the patient's shoulder. For example, FIG. 1A shows that if the arm 10 were to rotate about a vertical axis, there is a high likelihood that the x-ray image detector 13 would contact the patient's shoulder. The gap d between the detector and the patient's shoulder is very tight. But, if the x-ray image detector 13 is moved further away from the source 12 so as not to contact the patient's shoulder during operation, it would affect image acquisition by drastically reducing the field of view of the system.
Accordingly, there is a need for an improved x-ray detector and x-ray source arrangement that retains a wide field of view for radiographic image acquisition, so that while a cone beam computed tomography system is operating, the x-ray detector and x-ray source do not come into contact with the patient.